Map display device, a memory medium and a map display method

1. A map display device, comprising: memory means for storing polygon map data; drawing processing control means for drawing a polygon map by reading the polygon map data from the memory means; and display means for displaying an output from the drawing processing control means, wherein the drawing processing control means is equipped with a function for determining a unit of a polygon map that should be drawn and draws a polygon map of the determined unit to distinguish between a plurality of unit levels, wherein the polygon map data has only one unit of polygon data stored with larger polygon map data units drawn from the one unit of polygon data.

2. The map display device according to claim 1 , wherein the drawing processing control means reads polygon map data within a predetermined range, including a range of display, from the memory means and display patterns of adjoining polygon maps which are drawn different from each other.

3. The map display device according to claim 1 , wherein the drawing processing control means determines a vehicle present position or a cursor present position and only polygon map data, including the detected present position, is read from the memory means and drawn.

4. The map display device according to claim 1 , further comprising input means for inputting a display scale, wherein the drawing processing control means determines a unit of a polygon map that should be drawn on the basis of the display scale input by the input means and draws a polygon map of the determined unit.

5. The map display device according to claim 4 , wherein the drawing processing control means reads polygon map data within a predetermined range, including a range of display, from the memory means and display patterns of adjoining polygon maps which are drawn different from each other.

6. The map display device according to claim 4 , wherein the drawing processing control means determines a vehicle present position or a cursor present position and only polygon map data, including the detected present position, is read from the memory means and drawn.

7. The map display device according to claim 1 , wherein the drawing processing control means draws a polygon map that is included in a range of display and of a largest unit.

8. The map display device according to claim 7 , wherein the drawing processing control means reads polygon map data within a predetermined range, including a range of display, from the memory means and display patterns of adjoining polygon maps which are drawn different from each other.

9. The map display device according to claim 7 , wherein the drawing processing control means determines a vehicle present position or a cursor present position and only polygon map data, including the detected present position, is read from the memory means and drawn.

10. A computer readable memory medium, wherein the computer readable memory medium stores therein a polygon map database, and programs for determining a unit of a polygon map that should be drawn and drawing a polygon map of the determined unit to distinguish between a plurality of unit levels, wherein the polygon map database has only one unit of polygon data stored with larger polygon map data units drawn from the one unit of polygon data.

11. A method for displaying a map, comprising: storing polygon map data; and displaying a polygon map by reading the stored polygon map data, determining a unit of a polygon map that should be displayed and displaying a polygon map of the determined unit to distinguish between a plurality of unit levels, wherein the polygon map data has only one unit of polygon data stored with larger polygon map data units drawn from the one unit of polygon data.